An eight-month deployment will be twice as long as originally planned, defense officials told NBC News on Monday.

The major shift in the Stennis deployment comes as Iran renewed its threat to shut down the Strait of Hormuz over tighter international sanctions and the possibility that Israel may launch pre-emptive airstrikes against Iran's nuclear facility.

About 40 percent of the world's seaborne oil exports pass through the strait.

The shift and extension of the Stennis deployment will allow the U.S. Central Command to keep two aircraft carriers in the Persian Gulf region, Gulf of Oman and North Arabian Sea, not only as a hedge against Iran, but also to support combat air operations over Afghanistan.